Classic academic answer: it depends.
I've been monitoring the (US) market for about a year and a half now. C30 motorhomes in good-very good condition (both mechanically and inside/outside) are usually
offered for roughly $5-8.000. Many seem to struggle selling them, though.
For instance,
this one has been for sale for a very long time now (C30 priced at $7.500, allegedly in "excellent condition").
I've seen a few go for more, but then the buyer seem to be a) liquid and b) very keen to have that particular piece.
The challenge is, one can get a full-size motorhome built on a C30
van chassis for much less ($2-4.000) in a significantly better condition. Thus, the buyer must really want a pickup-based motorhome AND willing to pay more (=minority).
Fords go much cheaper too. 